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resolv: Introduce struct resolv_context [BZ #21668]

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struct resolv_context objects provide a temporary resolver context
which does not change during a name lookup operation.  Only when the
outmost context is created, the stub resolver configuration is
verified to be current (at present, only against previous res_init
calls).  Subsequent attempts to obtain the context will reuse the
result of the initial verification operation.

struct resolv_context can also be extended in the future to store
data which needs to be deallocated during thread cancellation.
This commit is contained in:
Florian Weimer
2017-06-30 21:10:23 +02:00
parent 4e45d83c92
commit 352f4ff9a2
24 changed files with 1032 additions and 370 deletions
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93
resolv/compat-gethnamaddr.c
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@@ -67,6 +67,7 @@
# include <stdio.h>
# include <netdb.h>
# include <resolv/resolv-internal.h>
# include <resolv/resolv_context.h>
# include <ctype.h>
# include <errno.h>
# include <stdlib.h>
@@ -84,6 +85,9 @@ static u_char host_addr[16]; /* IPv4 or IPv6 */
static FILE *hostf = NULL;
static int stayopen = 0;
static struct hostent *res_gethostbyname2_context (struct resolv_context *,
const char *name, int af);
static void map_v4v6_address (const char *src, char *dst) __THROW;
static void map_v4v6_hostent (struct hostent *hp, char **bp, int *len) __THROW;
@@ -428,23 +432,31 @@ libresolv_hidden_proto (res_gethostbyname2)
struct hostent *
res_gethostbyname (const char *name)
{
struct hostent *hp;
struct resolv_context *ctx = __resolv_context_get ();
if (ctx == NULL)
{
__set_h_errno (NETDB_INTERNAL);
return NULL;
}
if (__res_maybe_init (&_res, 0) == -1) {
__set_h_errno (NETDB_INTERNAL);
return (NULL);
if (res_use_inet6 ())
{
struct hostent *hp = res_gethostbyname2_context (ctx, name, AF_INET6);
if (hp != NULL)
{
__resolv_context_put (ctx);
return hp;
}
if (res_use_inet6 ()) {
hp = res_gethostbyname2(name, AF_INET6);
if (hp)
return (hp);
}
return (res_gethostbyname2(name, AF_INET));
}
struct hostent *hp = res_gethostbyname2_context (ctx, name, AF_INET);
__resolv_context_put (ctx);
return hp;
}
compat_symbol (libresolv, res_gethostbyname, res_gethostbyname, GLIBC_2_0);
struct hostent *
res_gethostbyname2 (const char *name, int af)
static struct hostent *
res_gethostbyname2_context (struct resolv_context *ctx,
const char *name, int af)
{
union
{
@@ -457,11 +469,6 @@ res_gethostbyname2 (const char *name, int af)
int n, size, type, len;
struct hostent *ret;
if (__res_maybe_init (&_res, 0) == -1) {
__set_h_errno (NETDB_INTERNAL);
return (NULL);
}
switch (af) {
case AF_INET:
size = INADDRSZ;
@@ -485,8 +492,10 @@ res_gethostbyname2 (const char *name, int af)
* this is also done in res_query() since we are not the only
* function that looks up host names.
*/
if (!strchr(name, '.') && (cp = __hostalias(name)))
name = cp;
char abuf[MAXDNAME];
if (strchr (name, '.') != NULL
&& (cp = __res_context_hostalias (ctx, name, abuf, sizeof (abuf))))
name = cp;
/*
* disallow names consisting only of digits/dots, unless
@@ -558,8 +567,9 @@ res_gethostbyname2 (const char *name, int af)
buf.buf = origbuf = (querybuf *) alloca (1024);
if ((n = __libc_res_nsearch(&_res, name, C_IN, type, buf.buf->buf, 1024,
&buf.ptr, NULL, NULL, NULL, NULL)) < 0) {
if ((n = __res_context_search
(ctx, name, C_IN, type, buf.buf->buf, 1024,
&buf.ptr, NULL, NULL, NULL, NULL)) < 0) {
if (buf.buf != origbuf)
free (buf.buf);
Dprintf("res_nsearch failed (%d)\n", n);
@@ -572,11 +582,26 @@ res_gethostbyname2 (const char *name, int af)
free (buf.buf);
return ret;
}
struct hostent *
res_gethostbyname2 (const char *name, int af)
{
struct resolv_context *ctx = __resolv_context_get ();
if (ctx == NULL)
{
__set_h_errno (NETDB_INTERNAL);
return NULL;
}
struct hostent *hp = res_gethostbyname2_context (ctx, name, AF_INET);
__resolv_context_put (ctx);
return hp;
}
libresolv_hidden_def (res_gethostbyname2)
compat_symbol (libresolv, res_gethostbyname2, res_gethostbyname2, GLIBC_2_0);
struct hostent *
res_gethostbyaddr (const void *addr, socklen_t len, int af)
static struct hostent *
res_gethostbyaddr_context (struct resolv_context *ctx,
const void *addr, socklen_t len, int af)
{
const u_char *uaddr = (const u_char *)addr;
static const u_char mapped[] = { 0,0, 0,0, 0,0, 0,0, 0,0, 0xff,0xff };
@@ -592,10 +617,6 @@ res_gethostbyaddr (const void *addr, socklen_t len, int af)
struct hostent *hp;
char qbuf[MAXDNAME+1], *qp = NULL;
if (__res_maybe_init (&_res, 0) == -1) {
__set_h_errno (NETDB_INTERNAL);
return (NULL);
}
if (af == AF_INET6 && len == IN6ADDRSZ &&
(!memcmp(uaddr, mapped, sizeof mapped) ||
!memcmp(uaddr, tunnelled, sizeof tunnelled))) {
@@ -645,8 +666,8 @@ res_gethostbyaddr (const void *addr, socklen_t len, int af)
buf.buf = orig_buf = (querybuf *) alloca (1024);
n = __libc_res_nquery(&_res, qbuf, C_IN, T_PTR, buf.buf->buf, 1024,
&buf.ptr, NULL, NULL, NULL, NULL);
n = __res_context_query (ctx, qbuf, C_IN, T_PTR, buf.buf->buf, 1024,
&buf.ptr, NULL, NULL, NULL, NULL);
if (n < 0) {
if (buf.buf != orig_buf)
free (buf.buf);
@@ -673,6 +694,20 @@ res_gethostbyaddr (const void *addr, socklen_t len, int af)
__set_h_errno (NETDB_SUCCESS);
return (hp);
}
struct hostent *
res_gethostbyaddr (const void *addr, socklen_t len, int af)
{
struct resolv_context *ctx = __resolv_context_get ();
if (ctx == NULL)
{
__set_h_errno (NETDB_INTERNAL);
return NULL;
}
struct hostent *hp = res_gethostbyaddr_context (ctx, addr, len, af);
__resolv_context_put (ctx);
return hp;
}
compat_symbol (libresolv, res_gethostbyaddr, res_gethostbyaddr, GLIBC_2_0);
void